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The Moon is not capable of keeping an Earth like atmosphere, nor is it practical to keep satellites in lunar orbit. Which means all transportation and communication would need to be ground based. No airplanes, no satellites, no GPS, decreased radio communication, etc.

Xenon is a heavy, colorless, dense, odorless noble gas. You would not be able to breath it, but if you inhaled some it would not kill you. It is heavy enough to make a fairly stable atmosphere on the Moon. If you had enough of it you could fly a kite, fly a plane, or float a balloon. It is rare on Earth, but assuming you found an asteroid or other source of significant amounts of xenon, how much would you need to make atmospheric plane and/or balloon operations possible?

Note: The boiling point of xenon is 165 K and the asteroid belt seems to have a temperature of around 200 K, so finding a frozen ball of xenon seems unlike, but if we did, how much would we need?

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  • $\begingroup$ Your question might benefit from not being restricted to merely xenon. Rather you might simply want to ask what kind of feasible transportation and exploration methods would work on the moon (with or without humans). $\endgroup$
    – spacer
    Nov 6, 2015 at 12:28
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    $\begingroup$ Creating Moon atmosphere with xenon, just to make flight-based transportation available? What about developing genetic engineering to create dinosaurs, then a time travel system, breed dinosaurs, kill them, move them a good few million years back to their time and bury them, thus creating new oil fields to resolve the fossil fuel crisis? $\endgroup$
    – SF.
    Nov 6, 2015 at 12:39
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    $\begingroup$ @JamesJenkins: Solid at the collection point but gaseous on the Moon, where the conditions aren't that vastly different if the cargo is to be delivered in a reasonable timeframe (asteroid orbit approaching Earth orbit)... $\endgroup$
    – SF.
    Nov 6, 2015 at 15:17
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    $\begingroup$ Inhaling Xenon will make you loose conscious, it is used as a general anaesthetic, see Wikipedia. If there is no anaesthetist present, inhaling Xenon might kill you. $\endgroup$
    – Uwe
    Dec 3, 2017 at 11:25
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    $\begingroup$ @JamesJenkins I really like your question. I think all those comments are just distracting and should be cleaned up. I also applaud your patience! $\endgroup$
    – uhoh
    Nov 23, 2018 at 0:08

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First of all, while xenon would be the most stable due to its molecular weight being the largest of any elemental non-radioactive gas, there are other gases that would work as well. Sulfur hexafluoride would be a particularly interesting choice, and that should be easier than xenon to find.

Okay, that notwithstanding, how well would it work to fly in an atmosphere of xenon or similarly heavy gas? As a source, I am going to use XKCD's interplanetary Cessna flying chart, and Bernoulli's principle from Wikipedia. Of particular note are a few things. One is that the ability to fly largely depends on the pressure, not on the weight of the gas. So you would need a whole lot of gas, making the atmosphere quite heavy (ideal gas law). You would then be able to fly, but only rocket powered items, which would probably be easier to do without the atmosphere anyways, although precision landing would be easier.

The other advantage of an atmosphere would be the protection against small micro-meteors, which is one of the major obstacles of lunar colonies. The temperature would also be somewhat regulated, etc. However, I still wouldn't recommend this.

Bottom line, I'd invest in some kind of high speed train, which should be much cheaper and easier to manage than filling the atmosphere with xenon.

enter image description here

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    $\begingroup$ If the gas was flammable, you could still fly on jet engines; you'd just load up on oxidizer instead of fuel. $\endgroup$
    – SF.
    Nov 6, 2015 at 13:37
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    $\begingroup$ True enough. The two best gases (Xenon and Sulfur hexafluoride) are not flammable, but I suppose a heavy hydrocarbon gas could be used. But that heavy gas would tend to be more susceptible to solar wind ionization, not to mention burning the gas would make it smaller and thus more susceptible to leaving the atmosphere. $\endgroup$
    – PearsonArtPhoto ♦
    Nov 6, 2015 at 13:55
  • $\begingroup$ I wouldn't worry about the last part though considering volume present:burnt ratio. $\endgroup$
    – SF.
    Nov 6, 2015 at 13:57
  • $\begingroup$ If we are worried about using Xenon to keep the atmosphere around, I would think the burnt ratio would be an influencer as well. $\endgroup$
    – PearsonArtPhoto ♦
    Nov 6, 2015 at 13:59
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    $\begingroup$ Sulfur Hexafloride as a means to create a dense and non reactive atmosphere might sound like a fun idea because of it's high density and it's harmless to breath, but UV rays from space would split up the molecule and create some free Fluorine, which is highly toxic and some SF5, which would likely form into small amounts of S2F10, which is highly toxic and stable, so it could become a permanent part of the atmosphere as it could form slowly but not break up as quickly, so, I'm not sure SF6 would work, unfortunately. en.wikipedia.org/wiki/Disulfur_decafluoride $\endgroup$
    – userLTK
    Mar 4, 2019 at 20:30

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